Treatment of argentiferous sulphide ores



Patented May 26, 1925 UNITED STATES PATENT OFFICE.

FRANKEDWARD ELMORE, 01 BOXMOQB, ENGLAND, ASSIGNOB, TO NIE S G. CHRISTEN SEN, F SALT LAKE GITY, UTAH.

TREATMENT OF ARGENTIFEROUS SUIJBHIDE ORES.

No Drawing.

To all whom it may concern:

Be it known that I, FRANK EDWARD EL- Momi, a subject of the King of Great Britain, residing in Boxmoor, England, have in- 5 vented certain new and useful Improvements in the Treatment of Argentiferous sulphide Ores, of which the following is a specification. 5

This invention relates to improvements in the treatment of argentiferous sulphide ores, concentrates and the like (hereinafter called ores) for the separation and recovery of the silver and other metals contain-ed therein.

In British patent specification No. 127,641 I have described a process (hereinafter called the acid brine process) for the separation of lea-d and zinc from ores in which these metals co-exist in the form of Sulphides, the said process consisting in treating .the finely divided ore with a hot strong solution of sodium chloride to which a suflicient quantity of sulphuric or hydrochloric acid or an alkali bisulphate is added, whereby the lead is caused to pass into solution whilst substantially the whole of the zinc sulphide remains undissolved, the hot solution obtained being separated from the residue containing the undisso-lved zinc sulphide and cooled to cause a partial crystal lization of the lead salt.

Ores suitable for treatment by the afore said process frequently contain appreciable proportions of silver, the efficient recovery of which by hitherto known methods of extraction is attended with difficulties. On treatment of the ore with acid brine only a portion of the silver passes into solution along with the lead. This portion may be recovered by known methods, but the balance remains undissolved with the zinc sulphide in the residue. The object of the present invention is to provide a satisfactory method of separating and recovering in form suitable for metallurgical treatment sub 45 stantially the whole of the silver and also, if desired, the lead and zinc contained in such orcs. In certain cases theore may be poor in lead and zinc and yet rich enough in silver to be worth treatment for the recovery of this metal alone.

According to this invention, if the urgentiferous ore or the argeutiferous residue containing zinc sulphide obtained therefrom by the acid brine process (which residue is hereinafter intended by the words argentiferous Serial No. 356,391.

residue) is heated under such conditions that the zinc sulphide remains substantially unchanged, the silver compounds which it contains become soluble in the solvent. Thus there is the technical advantage that the silver recovery may be enhanced Without defeating the object of the treatment with the solvent, namely the separation of the lead sulphide from the zinc sulphide wihout substantial alteration of the latter. The increased solubility of the silver compounds is brought about whether the ore itself is heated or the zinc sulphide residue which is left after extracting the lead is heated. In the former case it is of no importance if "0 the lead sulphide suffer oxidation, it is only essential that the zinc sulphide should remain substantially unaffected.

Therefore, according to this invention the ore itself, or the arg-entiferous residue containing zinc sulphide obtained, is-subjected to a suitable heat treatment as hereinafter described, and the silver and lead are then extracted by means of suitable solvents which leave the zinc sulphide substantially undissol ved. In some cases the ore after heat-treatment is subjected to the acid brine process and the argentiferous zinc-sulphide residue obtained is then without further heat-treatment leached by means of the said solvents. The silver passing into solution is recovered by known methods; the lead may also be recovered by known methods and the desilverized zinc sulphide may be subjected to metallurgical treatment as desired.

The suitable solvents aforesaid consist of hot, strong solutions of sodium chloride, calcium chloride or magnesium chloride con taining relatively small proportions of acid chloride. By the term acid chloride as hereinafter used and in the claims appended hereto I intend to include hydrogen chloride, a metallic chloride of an acid nature, and such metallic chloride associated with hydrogen chloride. rated solution of sodium chloride or a solution containing approximately 35 per cent by Weight of calcium chlorideor magnesium chloride, to which has been added a small percentage (varying with the composition 105 of the material to be leached) of cupric chloride, hydrochloric acid; or both. In cases'where the ore after heat-treatn1ent is not subjected to the acid-brine'process, I prefer to use a solvent containing about 3-5 110 I prefer to use a satu- I into lead' chloride the lead in the material to be leached, after allowing for other acidconsuming constituents, if any present, in The IEOI'IDZIUOII of zinc chloride is the ore. thus reduced to a minin'ium, whilst satisfactory extractions of the silver andv lead are effected-1 T hesuitable: heat treatment: aforesaid con si'sts,'.accordingrto one form oft-he invention, in heatingthe. ore or the argentiferous residue to; about a dultred: heat: a temperatune ofab out"500$ to600 G. being commonly' suitable) in, a zclosed or open vessel orin an atmosphene of-J neutral or reducing, gas for a short per'ioch: for exampleabout 1 hour; This treatment" greatly enhancesthe extractability oitw the'siliver by: the solvents aforesaid; ltselfect' does not appearto be dependentnponi the oxidation: of? any of. the sulphidesof-i lead oni zines: satisfactory resnlts havegbeen: obitrainedbythe preferred method of heating-' the one orangentiferous residliei alone in -a closed-vessel ,1 as Well :as'by heating it in an-opienivessehlalthough in the latter casei'much ofi thee lead sulphide and a relatively small: pontiion of the zinc sulphide may become oxidized. The heating: of: the ore has also beencarried out. in; presence of v canbon: dioxide, carbom monoxide hydrogen andnitzrogeng With satisfactory results,' but I prefer: the method of heating in a closed vessel:

The following areexamples'of'the manner in: which the invention may be performed. 1

Emample: Ai.An* argentiferous lea'd zinc sl'i'lphi'de ore from Burmah is treatedwith hot strongbrine'an'd sulphuric acid in the niarrnen'in'dicated I in- Example" 2.: of" my aforesaid British-r spncifi'catiom Nor 127 641. Them are 'thus obtained,1 on' the'one hand, an undisso'lved-f residue*containingzinc sul p hide' and a portion of' the 'silzver and, on the other, a: hotsolution: C011t2ll11ll1gtl10 lead and thebalanoe 'ofthe silverr The silver in the solution' may' be: recovered. by known methods as the brine is in practice'nsed nepeatedlyr I; prefer to: cool tl1c-solution','.col-

-lectthewlepositedlead-salts and treat the'lat- -ten to concentrate and recover .lIll the form about 1 hour, and. is allowed-to (5001:. It is then-tneatedv with. a solvent consisting; of a hot, strong soh'rtiion ofwcalciunr chloride-containing about'35' pen cent of'G-aGl and about 5 perrcentofcupric chloride,-"whereby sub-- stamtially: alh the: silver: is extracted from the residue. Thus a residue containing 1816 ounces of'silverper tmr was leached for about 1 hour at 90 C. with the acid solvent in the proportion of 1 gallon of liquid per pound 'of residue, 88 per cent of the silver being extractedl A similar residue, containing: 23' ounces of, silver per ton, when leachedin the same maner With a solution containing-3t) per: cent of calcium chloride, 5 per cent of cupric chloride-and 3pm cent of commercial concentrated hydrochloric acid,.yie1ded 90 persccntof the silver to the solvent.

Emample ore of the-kind referred to in; Example isheated in, a closed pot co-650" 6.. for l honr. After. cooling and, if necessary grinding it is treated the acid brine process as indicated in the foregoingi example fon separation of the: lead and zine, the silver accompanying the lead salts being, afterwards; recovered. as therein stated. The argentiferous residue contain ingc zinc sulphide is then treated with. a hot solvent such/asdescribed, in Example A for extractionvof the silvergvthusa residue containing; 825- ounces of silver per ton, when leached --with. the calcinrn chloridecupric chloride solvent, yielded/94 per cent ofthe silver'tothe-latter. In another ex am ple an ore containing 21.9; ounces of silver perton was; heated, to 450 CI. for 45 minutes and then. treated by the acid brine process; the residue Was; leached at 9594-00 (3. halfanshonr with a; solution containing 35 per goent of calcium chloride andzabouto percent of commercial concentrated. hydrochloric acidgn and: the final zinciferous; residue was found to-ivconitain less than 5 percent of the silver originally present in the ore. v

Ema/mp1s- U .-The ore, after being heated inv a closed pot," is leached-with a solvent which extracts'practically the. Wholev of the lead and silver together, leaving; practical- 1y? allptherzino, sulphide undissolvedr. The treatment ot the: heatedone by the acid brine process, as in-Example B, is thus dispensed with. In this case the. solvent consists of arhot; strong, acid solution con-- taining about- 35 per cent of.- calciumor magnesium chlonideand-a quantity of hydrochloric acidl not greatly in excess of that required; to ensure the extraction of thesilver" and lead -presenta Thus anore from Y Barmah containing 16.5.' pen cent of lead,.40'.3per. cent of zinc and. 18.5 ounces ofsilver' per ton washeatedin a closed pot to 7 00 (infer 1i hour andwasthen leached for- 3O minutes; at'about 95f Q. with-thesaid solvent in the proportion Of -134:4:t gallons of a 35. per cent solutiors of calcium chloride and 90. gallons of" commercial concentrated hydrochloric iacidvper ton of ore;v The residue contained 52% o cent/of zinc: and only a trace oflead? 9 S1lVeI' passed into the solvent.

45 per cent of the \Vhatever be the explanation of the effect of the heat-treatn'ient, it has been found that if the treatment be omitted a relatively small proportion of the silver is extracted by means of the solvents hereinbefore referred to.

The fineness to which the ore should be crushed, the temperature and duration of the heat treatment required, and the strength and quantity of the solutions used vary to some extent with the nature of the ore and other circumstances, but may readily be ascertained beforehand by trial on a laboratory scale. In some cases it may be advisable to subject the ore to a preliminary concentration with the object of reducing the proportion of acid-consuming or other objectionable material therein.

Having thus described the nature of the said invention and the best means I know of carrying the same into practical effect, I claim 1. Process for treating argentiferous leadzinc sulphide ores or argentiferous residue consisting in heating the material to about a dull red heat under conditions which as regards the zinc sulphide are substantially non-oxidizing whereby the zinc sulphide remains substantially undecomposed and then extracting the silver and lead by means of solvents which leave the zinc sulphide substantially undissolved.

2. Process of treating argentiferous lead zinc sulphide ores or argentiferous residue,

consisting in heating the material to about a dull red heat under conditions which as regards the zinc sulphide are substantially non-oxidizing whereby the zinc sulphide re mains substantially undecomposcd and then extracting the silver and lead by means of a solution of alkaline-earth chloride con taining acid chloride which leaves the zincsulphide substantially undissolved.

3. Process of treating argentiferous leadzinc sulphide ores or argentiferous residue, consisting in heating the material to about a dull red heat under conditions which as regards the zinc sulphide are substantially non-oxidizing whereby the zinc sulphide remains substantially undecomposed and then extracting the silver and lead by means of a solution of alkaline-earth chloride containing hydrogen chloride which leaves the zinc sulphide substantially undissolved.

4. Process of treating argentiferous leadzinc sulphide ores, consisting in heating the ore to about a dull red heat under conditions which as regards the zinc sulphide are substantially non-oxidizing whereby the zinc sulphide remains substantially undecomposed and then leaching the ore Which has been thus heated with a hot solution containing about 35 per cent of alkaline earth chloride and a quantity of hydrochloric acid not greatly in excess of that required to convert the lead sulphide into chloride, whereby the silver and lead are extracted together and the zinc sulphide is left substantially undissolved.

In testimony whereof I have signed my name to this specification.

FRANK EDWVARD ELMORE. 

